caffeine

noun

caf·​feine ka-ˈfēn 

ˈka-ˌfēn

: a bitter alkaloid C₈H₁₀N₄O₂ found especially in coffee, tea, cacao, and kola nuts and used medicinally as a stimulant and diuretic

Examples of caffeine in a Sentence

Her doctor told her to avoid caffeine.

Recent Examples on the Web

Maintaining a consistent sleep schedule, limiting screen exposure before bed, keeping the bedroom cool and dark and avoiding caffeine late in the day can all make a meaningful difference. —Allison Palmer, Sacbee.com, 16 Apr. 2026

For the most part, decaf coffee has the same chemical makeup as regular coffee, meaning the health benefits are similar except for those associated with caffeine. —Jeff Wagner, CBS News, 15 Apr. 2026

Made with peptides, collagen, caffeine, and cocoa seed extract — among other high-quality ingredients — this balm is proven to improve the skin’s texture and minimize the appearance of wrinkles and fine lines in four weeks. —Averi Baudler, PEOPLE, 15 Apr. 2026

Simon said the effect went far beyond caffeine. —Nick El Hajj, USA Today, 15 Apr. 2026

Word History

Etymology

German Kaffein, from Kaffee coffee, from French café

First Known Use

circa 1823, in the meaning defined above

Phrases Containing caffeine

• caffeine-free

Rhymes for caffeine

• agin
• alkene
• allene
• ameen
• amin
• amine
• arene
• athene
• baleen
• beeline
• benzene
• between

Kids Definition

caffeine

noun

caf·​feine ka-ˈfēn 

ˈka-ˌfēn

: a bitter stimulating compound found especially in coffee, tea, cacao, and kola nuts

Medical Definition

caffeine

noun

caf·​feine ka-ˈfēn, ˈka-ˌ; ˈkaf-ē-ən 

: a bitter alkaloid C₈H₁₀N₄O₂ found especially in coffee, tea, and kola nuts and used medicinally as a stimulant and diuretic

caffeinic

ka-ˈfē-nik  ˌkaf-ē-ˈin-ik 

adjective